How Many Minutes Should You Use Red Light Therapy For? Why Time is So Important.
How long should you use red light therapy? We know that the amount of time is connected to the dose of photobiomoduation. Which is critical to proper use and effectiveness.
But we think that time plays a much bigger role in effectiveness than you are being told.
A quick recap, here is the simple formula for red light therapy dosing.
Dose (J/cm^2) = Intensity (mW/cm^2) ÷ 1000 * Time (Seconds)
Theoretically, we could just focus what we call the dose.
Two-Dimensional Dosing Theory:
The dose relates to the biological effect of red light therapy.
- Too little dose gets no response.
- Too much dose gets an inhibitory response.
- In the middle, a stimulatory response.
You might have seen this dosing curve, which also describes the biphasic dose response curve.
Usually we want to land our dose somewhere in the peak of that stimulatory range when timing our doses. This way to get the cellular benefits that are often talked about with red light therapy.
Is going faster better?
The Bunsen-Rosco Law of reciprocity implies that you can achieve the same results as long as you reach the proper dose, regardless of intensity or time.
In terms of time, this means we could:
- Use a high intensity for a short amount of time.
- Use a low intensity for a longer amount of time.
Both ways would theoretically produce the same effect.
This theory is a marketing gold mine - since companies can easily market high intensity panels and claim they offer a theraputic dose faster.
Who wouldn't want to "save time" by getting a high intensity panel? Unfortunately, we are missing an entire dimension to this theory.
Can you Have Too Much?
The old adage goes "too much of a good thing can be bad for you" - is certainly true for red light therapy.
As seen in the Biphasic Dose curves, higher doses induce an "inhibitory" reaction from the cells. This does NOT mean there is an adverse effect, however it seems to negate or blunt the benefits we are seeking.
In fact, some authors note that in some therapeutic contexts like inducing analgesia, an inhibitory dose is desirable. So it is not always a bad thing.
So, as long as there is no significant heating from the light exposure, long treatment times are not harmful, but may be counterproductive if you are seeking a long-term benefit from the stimulation response.
Clinical Study that Breaks the Rule:
A clinical study using the Generation 2 Joovv Elite panel system tested the effects on young athletes.
The athletes were exposed to 5 minutes (2.5min each side) of treatment at 12 inches away.
The intensity was 46.17 mW/cm^2 and the dose they received was 6.9 J/cm^2.
Despite this dose being carefully mathematically calulated by the researchers to mimic the energy that was successful other trials, the study reported no significant improvement in the biomarkers they were looking for.
Of course there are many reasons why this study failed to produce a significant effect, but most people who are experienced in red light therapy would say that time of 5 minutes was too low.
Thus, the 2D theory of dosing is easily broken. And several authors and researchers clearly note that the usage of the Law of Reciprocity is problematic.
"The time course over which this is delivered is also important. Mathematical reciprocity of exposure time and irradiance to achieve a specific light dose can be ineffective or be deleterious."
And this comment tells us that the Law of Reciprocity is an oversimplification of complex biological process to a simple math problem. Which can be misleading to researchers and people trying to understand proper dosing protocols.
Another study summarizes the problem with wanting more intensity and less time:
"photobiological responses of cells and tissue usually involve a sequence of interacting biological reactions making a linear dose-time relationship less likely" 
Obviously we can't use a simple linear (2 dimensional) calculation to understand the effectiveness of red light therapy.
3-Dimensional Dosing Theory:
Indeed, many simple theories don't work predictably when we are dealing with complex biological systems.
Researches have proposed theories of dosing where both Time and Intensity play an important role in effectiveness.
This transforms our simple dosing curve into a 3 dimensional curve!
This 3-D Biphasic Dose curve is created by GembaRed LLC to illustrate the similar curves as shown in this study.
This curve now really emphasises how important time is for a biological response, and how closely it is connected to intensity.
Optimal Dosing Time:
The optimal dosage time is always highly dependent on the device parameters, what you are treating, and the individual's responsiveness to treatment.
We know that generally for skin-level treatment then shorter treatment times are used. For deeper-tissue treatment we need longer treatment times to allow an adequate amount of energy to reach those tissues.
What exactly is the ideal or optimal dose? We may not know yet since most dosing guidelines are centered around laser treatments. Although LED and laser perform similarly, there is a lot of context that changes between LED and laser devices.
Doing What Works:
We currently don't have a lot of studies that use large red light panels or full-body light therapy. Even if we did, proper dosing and timing is highly depending on the individual person's conditions and sensitivity.
And of course the intensity does play a very important factor when considering time, too much intensity would require us to always use a shorter treatment time. Which makes it harder to find that perfect "stimulation" range.
We find several successful studies using full-body light therapy had protocols ranging between 15 to 30 minutes. Shorter time-frames seemed to not deliver significant results.
For skin treatments the timing is often shorter, closer to 8-10 minutes.
Ultimately Red Light Therapy is something where we need to experiment and discover what works for you. But following the guidelines and concepts we present in our blogs will help empower people to find protocols that work for themselves.
We know that time is a critical aspect to calculating the energy delivered for a therapeutic dose of red light therapy. But it seems that time itself is often just as important as the energy.
The theories on Biphasic Dose response are updated with 3-Dimensional maps that include both intensity and time. This adds a dimension to dosing that most brands don't really talk about!
We know some logical theories for optimal dosing.
- Shorter times with high intensity devices
- Longer times with low intensity devices
And depending on the depth we want to treat, then we adjust the time accordingly.
- Shorter times to treat superficial areas.
- Longer times to treat deeper tissues.
Unfortunately, oversimplified marketing tactics that only focus on fallacies that "faster is better" may lead to a lack of results or effectiveness. Which also leads to the reason that most companies have to lie about thier intensity to be competitive.
In the future, becoming educated about red light therapy will mean investigating each individual parameter and variable, and finding the complex interactions that lead to clinical successes!
Huang YY, Sharma SK, Carroll J, Hamblin MR. Biphasic dose response in low level light therapy - an update. Dose Response. 2011;9(4):602-618. doi:10.2203/dose-response.11-009.Hamblin
James D Carroll
LLLT – DOSE RATE EFFECTS
Copyright 2008 THOR Photomedicine Ltd
A 3D dose model for low level laser / led therapy biostimulation and bioinhibition
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